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OBSERVATIONS ON THE HABITS OF THE 



ONUPHIDJ3 (POLYOTLETA), A XI.) ON THE 



INTERNAL STRUCTURES WITH 



WHICH THEY FORTIFY 



THEIR HOMES. 



By Arnold T. Watson, F.L.S. 

 (With a Plate). 



(Road 20th February, 1903.) 



The Onuphidje are marine bristle-footed worms, vary- 

 ing in the British species from, say, one to four inches 

 in length, some of the foreign species being much larger. 



They are somewhat centipede-like Annelids. The body 

 consists of a considerable number of segments, the first of 

 which is a well-defined head, with conspicuous eyes, and 

 several tentacles directed more or less forward. The 

 second segment contains the mouth, with its swollen palps 

 and complicated, savage-looking jaws ; then follow a great 

 number of segments, each swelling out on either side, to 

 form the para-podium, a lobe through which pass and 

 protrude laterally bristles of various kinds, which need 

 not now be particularised, beyond saying that some are 

 much stronger than others, and forceps-like at their outer 

 extremity. The first pair of parapodia (for reasons which 

 will appear later) have a forward direction ; the succeed- 

 ing feet stand out laterally, more or less at a right angle 

 to the body. All are capable of a muscular rowing move- 

 ment, like the oars in a boat. The body is reddish-yellow, 

 and iridescent, and diminishes in size towards the posterior 

 extremity, which terminates with . a pair of thread-like 



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